A self-healing hydrogel electrolyte based on carboxymethyl cellulose with synergistic structural reinforcement and ion transport regulation for flexible zinc-ion batteries

Abstract

Achieving a synergistic combination of high mechanical strength, autonomous self-healing capability, and tunable Zn²⁺ transport behavior within aqueous zinc-ion hydrogel electrolytes remains a critical challenge. Herein, a synergistic multi-regulation strategy is proposed to fabricate a multifunctional quasi-solid-state hydrogel electrolyte (CMC-B-0.2) utilizing carboxymethyl cellulose (CMC) and borax. This design leverages a dynamic reversible network constructed from borate ester bonds, Zn²⁺-carboxylate coordination, and hydrogen bonding. Specifically, the resulting CMC-B-0.2 hydrogel integrates superior mechanical strength, rapid autonomous self-healing properties, and swelling inhibition capabilities, thereby ensuring structural integrity under mechanical deformation. Simultaneously, the borate ester-derived B–O functional groups enable precise regulation of ion transport by reconstructing the Zn²⁺ solvation sheath, significantly lowering the desolvation energy barrier and homogenizing the interfacial ion flux. Consequently, the electrolyte demonstrates exceptional electrochemical performance: Zn//Zn symmetric batteries utilizing the CMC-B-0.2 hydrogel achieve dendrite-free stable cycling for over 3400 h, while flexible Zn//MnO₂ full batteries exhibit outstanding rate capability, cycling stability, and mechanical durability. This study presents a hydrogel electrolyte design strategy that unifies mechanical reliability with ion kinetics regulation, providing novel insights for the development of high-safety, long-lifespan, flexible aqueous zinc-ion batteries.